Health Assessment Document for Diesel Emissions - NSCEP | US ...

1 monkeys there were no specific histopathological effects reported (see next section) although
2 particle aggregates were reported in the distal airways, suggesting more small airway deposition.
3 Gross (1981) exposed rats for 20 h!day, 5.5 days/week for 87 weeks to diesel exhaust
4 containing 1.5 mg/m 3 particulate matter. When the data were normalized (e.g., indices expressed
5 in units of airflow or volume for each animal by its own forced expiratory volume), there were
6 no apparent functionally significant changes occurring in the lungs at 38 weeks of exposure that
7 might be attributable to the inhalation of diesel exhaust. After 87 weeks of exposure, functional
8 residual capacity (FRC).and its component volumes (expiratory reserve [ER] and residual
9 volume [RV]), maximum expiratory flow (MEF) at 40% FVC, MEF at 20% FVC, and FEV 0 _ 1
1 0 were significantly greater in the diesel-exposed rats. An observed increase in airflow at the end
11 of the forced expiratory maneuver when a decreased airflow would be expected from the
12 increased FRC, ER, and RV data (the typical scenario of human pulmonary disease) showed
13 these data to be inconsistent with known clinically significant health effects. Furthermore,
14 although the lung volume changes in the diesel-exposed rats could have been indicative of
15 emphysema or chronic obstructive lung disease, this interpretation was contradicted by the
16 airflow data, which suggest simultaneous lowering of the resistance of the distal airways.
17 Heinrich et al. (1982) evaluated the pulmonary function ofrats exposed to a concentration
18 of3.9 mg/m 3 particulate matter for 7 to 8 h!day, 5 days/week for 2 years. When compared with a
19 control group, no significant changes in respiratory rate, minute volume, compliance, or
20 resistance occurred in the exposed group (n,umber of rats per group was not stated).
21 Hamsters (eight or nine per group) were exposed 8 h!day, 7 days/week, for 6 mo to
22 concentrations of either about 6 mg/m 3 or about 12 mg/m 3 particulate matter (Vinegar et al.,
23 1980, 1981a,b). Vital capacity, vital capacity/lung weight ratio, residual lung volume by water
24 displacement, and C0 2 diffusing capacity de.creased significantly in hamsters exposed to
25 6 mg/m 3 particulate matter. Static deflation volume-pressure curves showed depressed deflation
26 volumes for diesel-exposed hamsters when volumes were corrected for body weight and even
27 greater depressed volumes when volumes were corrected for lung weight. However, when
28 volumes were expressed as percentage of vital capacity, the diesel-exposed hamsters had higher
29 lung volumes at 0 and 5 em H 20. In the absence of confirmatory histopathology, the authors
30 tentatively concluded that these elevated lung volumes and the significantly reduced diffusing
31 capacity in the same hamsters were indicative of possible emphysematous changes in the lung.
32 Similar lung function changes were reported in hamsters exposed at 12 mg/m 3 particulate matter;
33 but detailed information was not reported. It was stated, however, that the decrease in vital
34 capacity was 176% greater in the second experiment than in the first.
211/98 . 5-32 DRAFT--DO NOT CITE OR QUOTE